Recently, a new class of thermoelastic sulfonated polymers has been described in a number of U.S. patents. These sulfonated polymers are derived from polymeric materials having olefinic unsaturation, especially elastomeric polymers such as Butyl and EPDM rubbers. U.S. Pat. No. 3,642,728, herein incorporated by reference, clearly teaches a method of selective sulfonation of olefinic unsaturation sites of an elastomeric polymer to form an acid form of a sulfonated elastomeric polymer.
The olefinic sites of the elastomeric polymer are sulfonated by means of a complex of a sulfur trioxide donor and a Lewis base. The SO.sub.3 H groups of the sulfonated elastomer can be readily neutralized with a basic material to form an ionically cross-linked elastomer having substantially improved physical properties over an unsulfonated elastomer at room temperature. However, these ionically cross-linked elastomers, may be processed like a conventional thermoplastic at elevated temperatures under a shear force in the presence of selected preferential plasticizers which dissipate the ionic associations at the elevated temperatures thereby creating a reprocessable elastomer.
The basic materials used as neutralizing agents are selected from organic amines or basic materials selected from Groups I, II, III, IV, V, VI-B, VII-B and VIII and mixtures thereof of the Periodic Table of Elements. Although these sulfonated elastomeric polymers prepared by the process of this patent--are readily useable in a certain number of limited applications, they are deficient in properties compared to the improved compositions of the present invention.
U.S. Pat. No. 3,836,511, herein incorporated by reference, teaches an improved process for the sulfonation of the olefinic sites of the elastomeric polymer, wherein the improved sulfonating agent is selected from the group consisting of acetyl sulfate, propionyl sulfate and butyryl sulfate. The neutralizing agents employed to neutralize the acid form of the sulfonated elastomeric polymers are organic amines.
U.S. Pat. No. 3,870,841, herein incorporated by reference, teaches a method of plasticization of the polymeric backbone of a neutralized sulfonated plastic polymer by means of a polymer chain plasticizer which is a liquid compound having a boiling point of at least about 120.degree. F. The polymer chain plasticizer is selected from a dialkylphthalate, a process oil or an organic acid ester. Additionally, a domain plasticizer can be incorporated into the composition, wherein the domain plasticizer reversibly disrupts the association of the sulfonated groups at a temperature of forming.
U.S. Pat. No. 3,847,854, herein incorporated by reference, teaches a method of improving the processability of neutralized sulfonated elastomeric polymers by the addition of a preferential plasticizer which has at least one functional constituent which exhibits a bond moment whose absolute value is at least 0.6 Debyes, and must be a liquid at the desired processing temperature of the neutralized sulfonated elastomeric polymer.
Those references have taught that excellent elastomeric properties are attainable from Sulfo-EPDM, yet at the sulfonate levels desirable from a property viewpoint, the resulting materials are intractable in the absence of useful plasticizers.
A number of techniques have been considered as routes to overcome the lack of acceptable processability, including blending of sulfonated elastomers with crystalline polyolefins, polystyrenes and sulfonated polystyrenes. It was claimed that some improvements in flow behavior were observed in the presence of such polymers. Unfortunately polystyrene or sulfonated polystyrene are not compatible with Sulfo-EPDM or EPDM and, therefore, the resulting blends can exhibit poor and often irreproducible properties due to this incompatibility. There is a strong incentive to improve this compatibility for reasons that are described subsequently in this specification. The present invention describes an approach which optimizes the interactions between sulfonate containing polymers and polymers which are normally incompatible such that the properties of these blends are improved markedly over those previously described in the prior art.
It is an object of this invention to provide a process for blending homogeneously, in a wide range of proportions, synthetic polymers which have hitherto been regarded as incompatible. Another object is to provide a process for blending synthetic rubbery copolymers and synthetic hard resinous polymers at an elevated temperature in a device such as a mill. A still further object is the provision of thermoplastic blended molding compositions which can be molded to form products which are strongly resistant to fracture on impact.
It is a further object of this invention to achieve free flowing powdered compositions based on different polymer backbones which can be blended in the powdered form to create uniform compositions capable of being injection molded or extruded.
U.S. Pat. No. 3,236,914 has taught that a blend of a polymer containing a minor amount of carboxylic acid and a second polymer containing basic nitrogen atoms can lead to homogeneous blends of synthetic polymers. It is important to note that the blends of that patent were based on the interaction of acid and base components. Similarly, Eisenberg et al (Polymer Eng. and Sci., 22 (17), 1117, 1982) have reported that the combination of a polymer such as polystyrene containing 5 mole percent sulfonic acid groups is combined with a second polymer such as ethyl acylate containing 5 mole percent vinyl pyridine, the resultant acid base reactions compatibilize the blend of these polymers.
While these aforementioned blends are based on acid-base interactions, the preferred compositions of the instant invention are based on the interaction of polymers containing neutralized sulfonate, carboxylate or phosphonate species and a second polymer containing basic nitrogen atoms. The problems of conversion arising from free acid species, the water sensitivity, the instability of those acid moieties are hereby circumvented in using neutralized components. In addition, the polymer complexes which are formed are different in the strength of the interaction from those systems derived from acid-base reactions.
The unique and novel improved compositions of the present invention overcome the deficiencies of the aforementioned U.S. patents and applications from both a rheological and physical properties aspect. The blend compositions of the present invention solve the problem of having a material which has both desirable rheological and physical properties for the manufacture of an elastomeric article such as a garden hose, wherein the extrudate of the resultant compositions do not exhibit melt fracture during extrusion processing as is the case in some of the aforementioned patents.